Intellivision no picture/no signal provlem

I bought an intellivision motherboard from this guy on ebay and the system worked fine for a while. I let it sit in my closet for a couple months, and now it doesn't work properly. I believe the it powers on just fine because I've checked the readouts from the ribbon and they seemed fine. Alas, no picture is my woe and i was wondering if anyone here had any suggestions. When i turn the system on the screen does nothing. I just get the blank blue screen that says no signal on my tv.